Hydraulic control system for variable delivery pumps



June 21,1949. RTUCKER 2,474,174

HYDRAULIC CONTROL SYSTEM FOR VARIABLE DELIVERY PUMPS Filed Sept. 10,1945 2 Sheets-Sheet 1 Ila-,1-

INVENTOR WARREN R. TUCKER ATTO RNEYS June 21, 1949. w. R. TUCKER2,474,174

HYDRAULIC CONTROL SYSTEM FOR VARIABLE DELIVERY PUMPS Filed Sept. 10,1945 2 SheetsSheet 2 :EIl3. 2 32 2a M INVENTOR WARREN R.TUcKE R 54 bATTO R N EYS Patented June 21, 1949 HYDRAULIC CONTROL SYSTEM FORVARIABLE DELIVERY PUMPS Warren R. Tucker, Dayton, Ohio, assignor toH-P-M Development Corporation, Wilmington, Del., a corporation ofDelaware Application September 10, 1945, Serial No. 615,313

'4 Claims.

1 This invention relates to a control system for reciprocating rams andespecially to press rams.

The object of the present invention is to provide an improved controlsystem for a reciprocating ram which substantially eliminates theconventional servomotor from a reversible pump thereby greatly reducingthe cost of the hydraulic system.

It is another object to provide a press operating system which iscontrolled by metering fluid from the retracting side of the ram andemploying the pressure so generated to adjust the pump stroke to varythe press ram speed.

It is another object to provide such a circuit which includes thefeature of slowing down the press ram on its advancing stroke.

It is another object to provide such a system in which the advancingspeed of the ram is automatically and adjustably controlled.

It is still another object to provide an all hydraulic control systemfor a press having slow down and speed control.

In most cases where a reversible variable delivery pump is employed in apress circuit the pump is operated for the greater portion of the timeon either full forward, full reverse or in neutral. It is customary toequip such a pump with a servomotor mechanism which is capable ofpositioning the pump shift ring so that any rate of delivery can'beobtained in either direction. Such servomotor mechanisms are expensiveand add considerably to the cost of the pump and system.

The present invention eliminates the major portion of the cost of thepump servomotor while retaining its most desirable operating features,namely, the shifting of the pump into full forward, full reverse,neutral, and in addition thereto provides for a restricted deliveryposition to effect a slow-down of the ram and a means for continuouslyadjusting the pump stroke in order to control the speed of the ram.

These and other objects will become more apparent upon reference to thefollowing description taken in connection with the accompanying drawingin which:

Figure 1 is a diagrammatic view of a press having a circuit according tothis invention;

Figure 2 is a view showing the pump servomotor of this invention; and

Figure 3 is a view showing an open center type four way valve and aservomotor which includes centering springs.

Structural arrangement Referring to the drawings; there is shown a pressram In which is reciprocably mounted in a cylinder 12 and isconnected bythe conduits l4 and IS with a reversible variable delivery pump [8. Thepump l8 includes a'shift ring which is attached to or is abutted by apair of rods 22 and 24 which extend through and abut the bored pistons26 and 28, respectively, which are reciprocably mounted in the cylinders30 and 32, respectively. It will be noted that when the pistons are bothunder pressure, as in Figure 1, they bottom in their respectivecylinders and, through the rods 22 and 24, hold the pump shift ring 20in its no delivery position.

The cylinder 30 is connected by a conduit 34 with one service port of afour-way valve 36, the other service port of which is connected by aconduit 38 with the cylinder 32. A pump 40 supplies pressure fluidthrough a conduit 42 to the inlet port of the four-way valve while aconduit 44 including a choke valve 46 is connected with the exhaustports of the said valve. The valve 36 comprises a valve member 48, theupper end of which terminates in a solenoid 50 and the lower end ofwhich at 52 is adapted for engagement by an arm 54 carried by the ramH]. In the position shown in the drawings the valve 36 directs pressurefluid to both of the cylinders 30 and 32 so that the pistons 26 and 28are bottomed in their cylinders and the pump is held in neutral;

The conduit 34 is connected by a conduit which includes a check valve 58and a normally closed two-way valve 60 with a normally closed port 62 inthe valve 64. The valve 64 also comprises an inlet port 68 which isconnected with the conduit 42 and a valve member 68 which is v urgedleftwardly by a spring and rightwardly by pressure standing in thechamber 10. The chamber Ill is connected with the press side of themetering choke 12 in the conduit l6 while the pump side of the saidchoke is connected with the chamber'l4 which opposes the chamber 10.

The port 62 may be elongated, as shown in Figure 1,-to permit a quantityof fluid to pass from the source 40 to the cylinder 30 in accordancewith the speed of the ram l0.

Operation In operation, a work cycle is started by energizing thesolenoid 50 whereupon the member 48 moves upwardly and exhausts thecylinder 30 while continuing to supply pressure to the cylinder 32. Thisshifts the plungers 22 and 24 and shift ring 20 rightwardly so thatpressure fluid is delivered through the conduit I4 to the advancing areaof the ram Ill. During the initial advancing stroke the ram l movesdownwardly as rapidly as the pump l8 draws fluid from-the push back areathrough the conduit it. When the ram III has advanced a predeterminedamount it engages and opens the valve 60. At this time the pressure dropacross the metering choke 1'2 has urged the valve member 68 rightwardlyso that the ports 60 and 62 are interconnected and pilot fluid isdirected through the conduit 56 and the conduit 34 into the cylinder 30and the pump shift ring is moved toward reduced delivery position. Thedelivery of the pump willbe reduced until the pressure drop across thechoke I2 is such that the flow of pilot fluid through the valve 64 isequal to the flow of exhaust fluid through the conduit 44 and choke 46.The speed of the ram is thus controlled at any predetermined speed afterthe said ram opens the valve 60 by the rate of metering fluid throughthe valve 12. l A retracting stroke is instituted by de-energizing thesolenoid 50 whereupon the pressure from the pilot pump is directed tothe cylinder 30 while the cylinder 32 is exhausted. At the end of theretraction stroke the arm 54 picks up the portion 52 and returns thevalve member 48 to the osition shown in the drawings. During theretraction stroke the valve 12 is made ineifec tive by the bypassingcheck 13.

The excess discharge of the pump in may be passed to the reservoirthrough the relief valve It at any time.

In Figure 2 the basic servomotor and servomotor control valveconstruction Figure 1 is illustrated separate from the press circuit.The elements of this view are numbered similarly to those in Figure 1except with the addition of a subscript a.

Figure 3 shows a modified form of servomotoi' and servomotor controlvalve in which the pilot pump discharge is bypassed to exhaust by anopen center type pilot valve when the press is in its retractedposition, and the main pump is centered by the springs 80 and 82. Theparts of Figure 3 which are similar to those of Figure 2 bearcorresponding numbers with the addition of a subscript b.

It will be understood that various modifications and arrangements instructure -could be made without departing from the spirit of myinvention and, accordingly, I desire to comprehend such modificationsand substitutions of equivalents as may be considered to come within thescope of the appended claims.

I claim:

1. In a hydraulic system; a reciprocable plunger having advancing andretracting areas; a fluid source connected to supply said areas; opposedfluid operable control means associated with said source operable toposition said source in full delivery in one direction or the other orto position said source in neutral; 2. pilot pump; a choke valve; valvemeans movable to connect said pump with one or the other or both of saidcontrol means; means selectively operable for actuating said valve toconnect said pump with one of said control means while exhausting theother through said choke valve for positioning said source to deliverfluid to said advancing means; and means for supplying a variablepressure to said other control means during the advancing movement ofsaid plunger comprising, valve means arranged between said pilot pumpand said choke valve and operable during the advancing movement of saidplunger for bypassing a portion of the delivery of said pilot pump toexhaust through said choke valve.

2. In a hydraulic system; a plunger having advancing and retractingareas; a fluid source connected to supply said areas; first and secondfluid operable control means associated with said source respectivelyoperable by fluid pressure to position said source to supply saidadvancing area or said retracting area and also operable when both areunder pressure o position said source substantially to halt the supplyto said motor; a choke valve; first valve means operable to supplyactuating fluid to said first or to said second control means whileexhausting the other thereof, through said choke valve; or to supplyactuating fluid to both of said control means; a source of pressure; asecond valve means responsive to a predetermined rate of discharge fromsaid retracting area to establish a connection from said source to theinlet of said choke restricted inversely as the speed of said plunger;and third valve means operated by said plunger during a predeterminedportion of the advancing movement thereof for completing saidconnection, whereby said source delivers through said choke valve toexhaust and supplies a variable pressure to said second control means.

3. In a hydrauli system; a reciprocable plunger having advancing andretracting areas; a fluid source connected to supply said areas; op-

posed fluid operable control means associated movable to connect saidpump with one or the other or both of said control means; meansselectively operable for actuating said valve to connect said pump withone or said control means while exhausting the other through said fluidflow-restricting member for positioning said source to deliver fluid tosaid advancing area; and means for supplying a variable pressure to saidother control means during the advancing movement of said plungercomprising, valve means arranged between said pilot pump and saidflowrestricting member and operable during the ad-= vancing movement ofsaid plunger for by-passing a portion of the delivery of said Pilot pumpto exhaust through said flow-restricting memher.

4. In a hydraulic system; a plunger having advancing and retractingareas; a fluid source connected to supply said areas; first and secondfluid operable control means associated with said source respectivelyoperable by fluid pressure to position said source to supply saidadvancing area or said retracting area and also operable when both areunder pressure to position said source substantially to halt the supplyto said motor; a fluid flow-restricting member; first valve meansoperable to supply actuating fluid to said first or to said secondcontrol means while ment thereof for completing said connection, 4

whereby said source delivers through said flowrestricting member toexhaust and supplies 9, var-- iable pressure to said second controlmeans.

. WARREN R. TUCKER.

The following references are file of this patent:

REFERENCES CITED of record in the UNITED STATES PATENTS Number Date NameErnst Sept. 19, 1933 Douglas Oct. 6, 1936 Clark July 18, 1939 RobinsonMar. 4, 1941 Wiedmann May 6, 1941 Wiedmann r Feb. 24, 1942

